The utility power is AC (alternating voltage and alternating current), while the power consumed by most electrical and electronic equipment is DC (direct voltage and direct current), hence there is need for an AC-to-DC power conversion. A suitable controlled PFC (Power Factor Correction) converter forces an input AC current wave shape to be sinusoidal, in phase, and proportional with input AC voltage thus resulting in desirable low harmonic content and maximum available real power drawn from the AC line.
FIG. 1 schematically shows a prior art PFC converter 50. which comprises a full bridge rectifier and a boost converter. The full bridge rectifier comprises diodes D1˜D4. The boost converter comprises an inductor L, a switch S, a diode D5 and an output capacitor C coupled as shown. FIG. 1 shows the typical topology of the PFC converter which is known to persons of ordinary skill in the art. The control circuit which keeps an input current in phase with an input voltage is not shown. The boost converter supplies power to a load R. The full bridge rectifier folds an AC line voltage into a uni-directional voltage and folds an AC line current into a uni-directional current. The boost converter converts the uni-directional voltage into a DC output voltage and converts the uni-directional current into a DC output current.
In addition to boost converter losses, the input alternating current passes through the two diodes of the full bridge rectifier for either positive or negative portion of AC cycle in the PFC converter 50. The diode is inefficient and will result in the high conduction loss.
So there is a need to solve the above problems.